108 lines
3.1 KiB
C++
108 lines
3.1 KiB
C++
/**
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* \file magvar.hxx
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* Magnetic variation wrapper class.
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*/
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// Written by Curtis Olson, started July 2000.
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//
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// Copyright (C) 2000 Curtis L. Olson - http://www.flightgear.org/~curt
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//
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// This program is free software; you can redistribute it and/or
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// modify it under the terms of the GNU General Public License as
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// published by the Free Software Foundation; either version 2 of the
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// License, or (at your option) any later version.
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//
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// This program is distributed in the hope that it will be useful, but
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// WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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// General Public License for more details.
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//
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// You should have received a copy of the GNU General Public License
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// along with this program; if not, write to the Free Software
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// Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
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//
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// $Id$
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#ifndef _MAGVAR_HXX
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#define _MAGVAR_HXX
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#ifndef __cplusplus
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# error This library requires C++
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#endif
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// forward decls
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class SGGeod;
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/**
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* Magnetic variation wrapper class.
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*
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* The SGMagVar class calculates the magnetic variation and dip for
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* any position, altitude, and time. It is a complete
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* re-implimentation of the NIMA WMM 2000 (not derived from their demo
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* code.)
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*
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* The SGMagVar class is really a simple wrapper around the core Ed
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* Williams code which does all the hard work. This class allows you
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* to crunch the math once and then do multiple polls of the
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* data. However, if your position, altitude, or time has changed
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* significantly, you should call the update() method to recrunch new
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* numbers.
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*/
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class SGMagVar {
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private:
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double magvar;
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double magdip;
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public:
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/**
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* This creates an instance of the SGMagVar object.
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* You must call the update() method before any queries will be valid.
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*/
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SGMagVar();
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/** Destructor */
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~SGMagVar();
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/** Recalculate the magnetic offset and dip.
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* The update() method requires you to pass in your position and
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* the julian date. Lon and lat are specified in radians, altitude
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* is specified in meters. Julian date can be conveniently
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* calculated by using an instance of the SGTime class.
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* @param lon longitude in radians
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* @param lat latitude in radians
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* @param alt_m altitude above sea level in meters
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* @param jd julian date
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*/
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void update( double lon, double lat, double alt_m, double jd );
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/**
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* overloaded variant taking an SGGeod to specify position
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*/
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void update( const SGGeod& geod, double jd );
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/** @return the current magnetic variation in radians. */
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double get_magvar() const { return magvar; }
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/** @return the current magnetic dip in radians. */
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double get_magdip() const { return magdip; }
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};
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/**
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* \relates SGMagVar
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* Lookup the magvar for any arbitrary location (This function doesn't
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* save state like the SGMagVar class. This function triggers a fair
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* amount of CPU work, so use it cautiously.
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* @return the magvar in radians
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*/
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double sgGetMagVar( double lon, double lat, double alt_m, double jd );
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#endif // _MAGVAR_HXX
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